The peritoneum is the largest serous membrane in the body. The part which lines the abdominal wall is named the parietal peritoneum; that which is reflected over the contained viscera constitutes the visceral peritoneum. The space between the parietal and visceral layers of the peritoneum is named the peritoneal cavity; but under normal conditions, this cavity is merely a potential one, since the parietal and visceral layers are in contact.
It is well-known that the peritoneal membrane will function effectively as an ion exchange membrane for various purposes. As early as 1923, peritoneal dialysis (an artificial kidney format) was first applied clinically. The first peritoneal access device was a piece of rubber tubing temporarily sutured in place. As early as 1960, peritoneal dialysis was becoming an established form of artificial kidney therapy for acute renal failure and, in order to lessen the discomfort of repeated, temporary punctures into the peritoneal cavity, acute or temporary peritoneal catheters were developed.
Conventionally, a peritoneal dialysis system involves introducing dialyzing fluids into the peritoneal cavity of the body by way of a catheter secured with a perforated end within the peritoneal cavity and the other end projecting through the epidermis. The dialyzing fluids is introduced into the body by opening the external end of the catheter and passing a dialyzing fluid through the catheter into the cavity for a specified time period and in quantities sufficient to permit endogenous wastes from the blood to diffuse across the peritoneal membrane using dialysis fluid to create a concentration gradient. The dialyzing fluid is then removed by siphon or a gravity technique and the procedure is repeated. This system is used to perform for both acute and chronic dialysis.
Presently, the standard methods of accomplishing peritoneal dialysis in patients with end stage renal disease are continuous ambulatory peritoneal dialysis ("CAPD") and continuous cyclic peritoneal dialysis ("CCPD"). CAPD is performed during the day, with a patient or his designee controlling both the inflow and drainage of the dialysis fluid. Typically, CAPD is done everyday and the in-flow and drainage is conducted four times with an average dwell time of approximately 1/2 to 2 hours for each cycle. In contrast, CCPD is performed by a machine connected to a patient, during the night while a patient sleeps, with a machine controlling the in-flow and drainage of the dialysis fluid. See, e.g., Report of National CAPD Registry of National Institute of Health, Lindblad et al., (1987).
In the conventional methods, the external end of the catheter exits through the epidermis where it is closed until required. This arrangement is frequently uncomfortable to a patient because the catheter projects permanently from the patient's body at some point in the abdominal wall. In addition, this system poses a serious infection problem. The open end of the catheter provides a permanent entrance for possible infection. Currently, the rate of peritonitis is 1.4 episodes per patient years. Peritonitis is an inflammation of the lining of the peritoneal cavity. It is believed that peritonitis may also be caused by microorganisms passing down the outer wall of the catheter, i.e. catheter tract, and through the biological barriers before these biological barriers have been fully integrated with the surrounding tissue.
In addition, the rate of exit site infections are 0.5 episodes per patient year for this conventional method. In an attempt to reduce infection, the patient must take a great deal of care in making sure the catheter is closed at all times when not in use and the area near the exit site of the catheter is always clean. Even with these precautions, microorganisms can enter the catheter. The patient, must be especially careful when taking a shower or swimming due to the increased risk of introducing infection through the catheter.
Moreover, in the conventional method, since the portion of the catheter exiting from the patient's body is normally held against the body with a bandage over a long period of time, there is always a potential source of localized skin problems caused by the adhesive bandage securing the catheter end. Furthermore, this exiting catheter also creates cosmetic and psychological problems for the patient. These psychological problems are particularly acute in patient with kidney problems that require many hours of dialysis every week for indefinite periods of time.
Recently, in an attempt to reduce infections and cosmetic problems associated with transepithelial catheters, injection ports have been developed which can be implanted in the body. Typically, these injection ports are used to administer medication to a patient by means of conventional hypodermic syringe.
Known injection devices of this general type have an injection chamber formed within a housing of cup-like configuration with a top end closed by a needle-penetrable, diaphragm. The diaphragm is typically located axially within a cylindrical channel formed near the open end of the housing. With this arrangement, the exposed surface of the diaphragm is generally recessed within the housing. The chamber conventionally is situated immediately below the diaphragm for receiving the medication. Typically, the medication is delivered to a desired site within the patient by means of catheter connected to a hollow stem leading from the chamber.
However, these conventional injection ports have the major disadvantage of not being capable of withstanding repeated puncturing by a needle. Moreover, since these injection ports are typically designed for administering medication, they are not suitable for applications requiring large flow rates such as peritoneal dialysis.
For example, a transcutaneous device as shown in U.S. Pat. No. 4,490,137, discloses a rigid metallic reservoir. The unyielding structure of the metallic reservoir can cause discomfort upon implantation. The device also includes a needle penetrable surface that is not self sealing. Consequently, upon withdrawal of the needle, a fluid path can be established causing leakage. There is also a possibility of reflux back along the surface of the needle during injection. Thus, this device would be totally unacceptable for any application requiring repeat usage.
In another example, subcutaneous injection sites disclosed in U.S. Pat. Nos. 4,543,088 and 5,045,060 include a needle penetrable diaphragm made of an elastic material of silicone rubber. The patents describe the sealing mechanism of the diaphragm as being established by wedging the diaphragm into the unit to provide elastic restoring forces of the silicone rubber within the diaphragm. However, with repeated punctures by large bore needles, the diaphragm loses its ability to seal which results in leakage. Moreover, due to the requirement of maintaining the diaphragm in a compressive state, the maximum size of the diaphragm is limited, and, thus, the unit would not be feasible for applications requiring large needles such as peritoneal dialysis.
In a further example, the implantable resealable puncture housing disclosed in U.S. Pat. No. 4,190,040 utilizes a laminated structure wherein a silicone gel is sandwiched between two silicone layers. Such a device did provide for a more varied angle of penetration for a hypodermic needle being inserted into the chamber. However, the housing is unacceptable for repeated puncturing with large bore hypodermic needles because gel bleeding can occur. In addition, such a device after repeated puncturing does not provide for effective sealing, particularly when the fluid in the chamber within the housing is under elevated pressures such as pressures at or near the blood pressure levels of a patient.